[Differential scanning calorimetry analyses of phase transformations in different nickel-titanium orthodontic wires].
OBJECTIVE
To characterize austenite, martensite and R phase temperatures as well as transition temperature ranges of the commonly used nickel-titanium (NiTi) orthodontic arch wires selected from several manufacturers.


METHODS
Differential scanning calorimetry (DSC) method was used to study the phase transformation temperatures and the phase transition processes of 9 commonly used NiTi alloys (types: 0.406 mm, 0.406 mm x 0.559 mm).


RESULTS
The austenite finish temperatures of A, B, D NiTi wires were 22.4 CT, 21.9 degrees C, 22.5 degrees C, respectively. No phase transformation was detected during oral temperature. It indicated that these types of NiTi wires did not possess shape memory property. For C and H NiTi wires, no phase transformation was detected during the scanning temperature range, suggesting that these two types of wires did not possess shape memory either. The austenite finish temperatures of E, G and I NiTi wires were 34.3 degrees C, 36.6 degrees C, 38.5 degrees C, respectively, which were close to the oral temperature and presented as martensitic-austenitic structures at room temperature, suggesting that the NiTi wires listed above had good shape memory effect. Although F NiTi wire also showed martensitic-austenitic structures at room temperature, its austenite finish temperature (61.5 degrees C) was much higher than oral temperature.


CONCLUSIONS
The transformation phase temperatures and transformation behavior were varied among different NiTi alloys, leading to variability in shape memory effect.
Bai
Yu-xing
YX
Department of Orthodontics, Faculty of Stomatology, Capital University of Medical Sciences, Beijing 100050, China. byuxing@263.net
Ren
Chao-chao
CC
Wang
Hong-mei
HM
Zheng
Yu-feng
YF
Wang
Yan-bo
YB
Li
Song
S
D002152:Calorimetry, Differential Scanning; D003722:Dental Alloys / Q000737:chemistry*; D008422:Materials Testing; D009969:Orthodontic Wires; D044367:Phase Transition; D013696:Temperature
D003722:Dental Alloys